US2891164A - Gas detector - Google Patents

Gas detector Download PDF

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US2891164A
US2891164A US402120A US40212054A US2891164A US 2891164 A US2891164 A US 2891164A US 402120 A US402120 A US 402120A US 40212054 A US40212054 A US 40212054A US 2891164 A US2891164 A US 2891164A
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gas
window
strip
housing
color
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US402120A
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Michael Paul Lee
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MSA Safety Inc
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Mine Safety Appliances Co
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/33—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using ultraviolet light

Definitions

  • the gas detector which is the subject of this invention, overcomes many of those disadvantages. For example, it is more sensitive to lower gas concentrations than the hot filament type of gas detector and is not handicapped by filament poisoning. It also can measure non-combustible mixtures.
  • the apparatus of this invention is not subject to excessive time consumption or to special preparations needed for most chemical methods. Also, it is adaptable to more gases than present colorimetric detectors and is not influence by sample flow. Finally, it does not require special preparations for each gas being analyzed.
  • a housing has a window in one side that will filter out ultraviolet rays.
  • the insideof the housing is provided with means for holding a thin strip of material, which is color-sensitive to ultraviolet rays, close to the window.
  • a source of ultraviolet energy is spaced a considerable distance from the housing window in a position to direct its rays toward the strip to change its color.
  • the strip preferably is long and wound on spools at opposite sides of the window.
  • the housing is adapted to receive a gas sample in the path of the rays between the energy source and strip.
  • Color standards are exposed to view beside the housing Window for matching with the color of the strip after it has been exposed to the ultraviolet rays for a predetermined period. The color standard that matches with the color of the strip indicates the concentration of any of the ultraviolet ray absorbing gas that is detected in the sample.
  • Fig. 1 is a plan view of my apparatus with part of the cover broken away;
  • Fig. 2 is a combined side view and vertical section
  • Fig. 3 is a cross section taken on the line IIL-III of Fig. 2.
  • a rectangular housing is formed from an open top box 1 that normally is closed by a snugly fitting cover 2.
  • the cover preferably midway between its ends, is provided with a rectangular opening, in which a window 3 is fitted.
  • This window is made of transparent material that will filter the ultraviolet rays out of the daylight to keep such rays from entering the housing through the window.
  • a suitable material for this purpose is a glass, No. 7380, manufactured by Corning Glass Company.
  • flanged spools are rotatably mounted in any suitable manner, such as like camera film spools.
  • the supply spool 5 contains a roll of thin strip material, such as paper 6, the color of which will change when exposed to ultraviolet rays.
  • the outer end of this sensitive strip is pulled from the supply spool and attached to the winding spool 7 at the opposite end of the housing.
  • the winding spool is provided with a knob 3 outside of the housing for turning the spool in order to wind the strip on it as desired.
  • An electrically operated source of ultraviolet energy 10 is mounted in the housing below the sensitive strip 6 and a considerable distance from the housing window, toward which it directs its rays.
  • a sample of the gas mixture to be analyzed for the purpose of determining whether a certain known gas is present in it, as well as the concentration of that gas, is admitted to the housing.
  • the gas being detected which includes vapor, must be one that will absorb ultraviolet rays. Examples are hydrogen sulfide, carbon tetrachloride, ammonia, water vapor, benzine, carbon monoxide, ether, mercury vapor, etc.
  • the ultraviolet rays from source 10 pass through a considerable portion of this sample before reaching the sensitive strip.
  • the gas that is being detected If the gas that is being detected is present, it will absorb ultraviolet energy in proportion to the amount of that gas in the sample. Thus, the greater the concentration of the gas in question, the more ultraviolet energy it will absorb and the lighter the color of the sensitive strip will appear. The color of the strip is changed completely through it, so that the change can be seen through window 3.
  • color standards which may be cards 12 and 13 of suitable material divided into sections show ing difierent shades of the color that the sensitive strip takes when exposed to ultraviolet rays.
  • the standards can be marked in percentages of gas concentration, so that a direct reading of the gas concentration in the sample can be made.
  • the sensitive strip should be held close to the inner surface of window 3 for good visibility, so means is provided for that purpose.
  • This means can be part of means for keeping the gas sample from coming in contact with the sensitive strip, which is desirable in. some cases, and for preventing the sample from leaking out of the housing between the box and cover.
  • the housing contains a chamber to which the gas sample is confined and by which the strip is held close to the housing window.
  • This chamber may have a fiat bottom wall 15 spaced from the bottom of the box, and an upper wall formed from two plates 16 and 17 extending from opposite ends of the box inward beneath the adjacent spools and then curving upward to points preferably close to the opposite edges of the housing window.
  • the spools are located in recesses formed between the top of the chamber and the housing.
  • the space between the upper ends. of the two curved plates is closed by a window 18 that will transmit ultraviolet rays from source 10 to the sensitive strip located between the two windows.
  • the lower window holds the strip close to the window above it.
  • the two windows are shown registering with each other, it is not necessary that they do so, in which case the strip would have to be moved from window 18 to window 3 after exposure.
  • an inlet tube 19 Joined to one end of the sample chamber is an inlet tube 19 that extends out through the end wall of the housing, while a similar tube 20 is connected to the opposite end of the chamber. Any well known means may be used for pumping or drawing gas samples into and out of the chamber through the two tubes.
  • the iiat'bottom wall of the gas chamber with a central rectangular opening sealed by an ultraviolet ray transmitting glass 22. Directly below this glass the source of ultraviolet energy is located. A curved reflector 23 extends beneath the source and helps to direct its rays upward through the chamber and window 18 to the sensitive strip.
  • a sample of a reference gas containing a known concentration of ray absorbing gas is delivered to the gas chamber.
  • the color of the sensitive strip as seen through window 3 is matched with the color standards.
  • the standard that matches the strip is marked with the percentage of the ultraviolet ray absorbing gas known to be in the sample.
  • the gas detector Before operating the gas detector, it is necessary to stabilize'the ultraviolet source by allowing it to warm up for a few minutes. A sample of gas then is drawn into the gas chamber and the winding spool is turned to draw an unexposed area of the sensitive strip into the space between the two windows. At the end of the prescribed exposure time, the presence and concentration of a particular gas can be determined by comparing the color of the strip with the color standards. Later a fresh gas sample can be admitted to the chamber and the sensitive strip can be moved to locate another unexposed area between the windows.
  • a gas detector for use in an atmosphere where it is known that only one ultraviolet ray absorbing gas may be present in an amount that can readily be detected
  • said detector comprising a housing provided in one side with a window that filters out ultraviolet rays, means in the housing adapted to hold close to the window a thin strip of material color-sensitive to ultraviolet rays, a constant source of ultraviolet energy in the housing spaced a considerable distance from said window in a position todirect its rays toward the strip to. change its color, said housing being adapted to receive in the path of the rays between said energy source and strip, a gas sample that may contain acertain ultraviolet ray absorbing gas, and color standards exposed to view beside the housing window for matching with the color of the strip after a predetermined exposure period, whereby to indicate whether said ultraviolet ray absorbing gas is present in the sample and its concentration therein.
  • a gas detector for use in an atmosphere where it is known that only one ultraviolet ray absorbing gas may be present in an amount that can readily be detected, said detector comprising a housing provided with a window in one side that filters out ultraviolet rays, a chamber in the housing for receiving a gas sample that may contain a certain ultraviolet ray absorbing gas, said chamber being provided in one side with an ultraviolet energy transmitting window adjacent said housing window, means for positioning outside of said chamber window a thin strip of material color-sensitive to ultraviolet rays, a constant source of ultraviolet energy in a position to direct its rays through the chamber and its window to change the color of the strip, and color standards exposed to view beside the housing window for matching with the color of said strip after a predetermined exposure time, whereby to indicate whether said ultraviolet ray absorbing gas is present in the chamber and its concentration therein.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
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  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)

Description

June 16, 1959 MlcHAEL 2,891,164
GAS DETECTOR Filed Jan. 4. 1954 INVENTOR. P0414 Lee- M a/95 vBY flaw, aw mwgg All: flr razelva'ys GAS DETECTOR Paul Lee Michael, Pittsburgh, Pa., assiguor to Mine Safety Appliances Company, Pittsburgh, Pa., a corporalion of Pennsylvania This invention relates to portable apparatus for detecting the presence and percentage of a particular gas in a sample of a gas mixture, and more part cularly to apparatus which uses ultraviolet energy to aid in the detection.
Most of the existing methods of gas analysis or detection fall into one of the following three classes:
(1) Physical. or physico-chemical methods.
(2) Adaptations of the ordinary methods of chemical analysis-volumetric analysis, etc.
(3) Colorimetric or nephelometric method.
A number of small portable detectors have been produced for practicing each of the methods just mentioned, but all of them have disadvantages. The gas detector, which is the subject of this invention, overcomes many of those disadvantages. For example, it is more sensitive to lower gas concentrations than the hot filament type of gas detector and is not handicapped by filament poisoning. It also can measure non-combustible mixtures. The apparatus of this invention is not subject to excessive time consumption or to special preparations needed for most chemical methods. Also, it is adaptable to more gases than present colorimetric detectors and is not influence by sample flow. Finally, it does not require special preparations for each gas being analyzed.
In accordance with this invention, a housing has a window in one side that will filter out ultraviolet rays.
United States Patent The insideof the housing is provided with means for holding a thin strip of material, which is color-sensitive to ultraviolet rays, close to the window. Inside of the housing a source of ultraviolet energy is spaced a considerable distance from the housing window in a position to direct its rays toward the strip to change its color. The strip preferably is long and wound on spools at opposite sides of the window. The housing is adapted to receive a gas sample in the path of the rays between the energy source and strip. Color standards are exposed to view beside the housing Window for matching with the color of the strip after it has been exposed to the ultraviolet rays for a predetermined period. The color standard that matches with the color of the strip indicates the concentration of any of the ultraviolet ray absorbing gas that is detected in the sample.
The preferred embodiment of the invention is illustrated in the accompanying drawings, in which:
Fig. 1 is a plan view of my apparatus with part of the cover broken away;
Fig. 2 is a combined side view and vertical section; and
Fig. 3 is a cross section taken on the line IIL-III of Fig. 2.
Referring to the drawings, a rectangular housing is formed from an open top box 1 that normally is closed by a snugly fitting cover 2. The cover, preferably midway between its ends, is provided with a rectangular opening, in which a window 3 is fitted. This window is made of transparent material that will filter the ultraviolet rays out of the daylight to keep such rays from entering the housing through the window. A suitable material for this purpose is a glass, No. 7380, manufactured by Corning Glass Company.
In the upper portions of the opposite ends of the box, flanged spools are rotatably mounted in any suitable manner, such as like camera film spools. The supply spool 5 contains a roll of thin strip material, such as paper 6, the color of which will change when exposed to ultraviolet rays. The outer end of this sensitive strip is pulled from the supply spool and attached to the winding spool 7 at the opposite end of the housing. The winding spool is provided with a knob 3 outside of the housing for turning the spool in order to wind the strip on it as desired.
An electrically operated source of ultraviolet energy 10 is mounted in the housing below the sensitive strip 6 and a considerable distance from the housing window, toward which it directs its rays. A sample of the gas mixture to be analyzed for the purpose of determining whether a certain known gas is present in it, as well as the concentration of that gas, is admitted to the housing. The gas being detected, which includes vapor, must be one that will absorb ultraviolet rays. Examples are hydrogen sulfide, carbon tetrachloride, ammonia, water vapor, benzine, carbon monoxide, ether, mercury vapor, etc. The ultraviolet rays from source 10 pass through a considerable portion of this sample before reaching the sensitive strip. If the gas that is being detected is present, it will absorb ultraviolet energy in proportion to the amount of that gas in the sample. Thus, the greater the concentration of the gas in question, the more ultraviolet energy it will absorb and the lighter the color of the sensitive strip will appear. The color of the strip is changed completely through it, so that the change can be seen through window 3.
Mounted on top of the housing cover on opposite sides of its window are color standards, which may be cards 12 and 13 of suitable material divided into sections show ing difierent shades of the color that the sensitive strip takes when exposed to ultraviolet rays. The color or shade of the exposed strip, as seen through the housing window, therefore can be compared with the color standards to match it with one of them. The standards can be marked in percentages of gas concentration, so that a direct reading of the gas concentration in the sample can be made.
The sensitive strip should be held close to the inner surface of window 3 for good visibility, so means is provided for that purpose. This means can be part of means for keeping the gas sample from coming in contact with the sensitive strip, which is desirable in. some cases, and for preventing the sample from leaking out of the housing between the box and cover. Accordingly, the housing contains a chamber to which the gas sample is confined and by which the strip is held close to the housing window. This chamber may have a fiat bottom wall 15 spaced from the bottom of the box, and an upper wall formed from two plates 16 and 17 extending from opposite ends of the box inward beneath the adjacent spools and then curving upward to points preferably close to the opposite edges of the housing window. Consequently, the spools are located in recesses formed between the top of the chamber and the housing. The space between the upper ends. of the two curved plates is closed by a window 18 that will transmit ultraviolet rays from source 10 to the sensitive strip located between the two windows. The lower window holds the strip close to the window above it. Although the two windows are shown registering with each other, it is not necessary that they do so, in which case the strip would have to be moved from window 18 to window 3 after exposure. Joined to one end of the sample chamber is an inlet tube 19 that extends out through the end wall of the housing, while a similar tube 20 is connected to the opposite end of the chamber. Any well known means may be used for pumping or drawing gas samples into and out of the chamber through the two tubes.
With this construction it is preferred to provide the iiat'bottom wall of the gas chamber with a central rectangular opening sealed by an ultraviolet ray transmitting glass 22. Directly below this glass the source of ultraviolet energy is located. A curved reflector 23 extends beneath the source and helps to direct its rays upward through the chamber and window 18 to the sensitive strip.
To calibrate this instrument for a particular ultraviolet rayabsorbing gas, a sample of a reference gas containing a known concentration of ray absorbing gas is delivered to the gas chamber. After passing ultraviolet energy from source through the gas for a predetermined time, such as 30 or 40 seconds, the color of the sensitive strip as seen through window 3 is matched with the color standards. The standard that matches the strip is marked with the percentage of the ultraviolet ray absorbing gas known to be in the sample. By repeating this operation for various known concentrations, the apparatus is calibrated to read the concentration of gas directly. It is notnecessary to change the color standards for each difierent gas that is to be detected, because several different gases may fall into a group that uses the same color standards.
Before operating the gas detector, it is necessary to stabilize'the ultraviolet source by allowing it to warm up for a few minutes. A sample of gas then is drawn into the gas chamber and the winding spool is turned to draw an unexposed area of the sensitive strip into the space between the two windows. At the end of the prescribed exposure time, the presence and concentration of a particular gas can be determined by comparing the color of the strip with the color standards. Later a fresh gas sample can be admitted to the chamber and the sensitive strip can be moved to locate another unexposed area between the windows.
According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.
I claim:
1. A gas detector for use in an atmosphere where it is known that only one ultraviolet ray absorbing gas may be present in an amount that can readily be detected,
said detector comprising a housing provided in one side with a window that filters out ultraviolet rays, means in the housing adapted to hold close to the window a thin strip of material color-sensitive to ultraviolet rays, a constant source of ultraviolet energy in the housing spaced a considerable distance from said window in a position todirect its rays toward the strip to. change its color, said housing being adapted to receive in the path of the rays between said energy source and strip, a gas sample that may contain acertain ultraviolet ray absorbing gas, and color standards exposed to view beside the housing window for matching with the color of the strip after a predetermined exposure period, whereby to indicate whether said ultraviolet ray absorbing gas is present in the sample and its concentration therein.
2. A detector as defined in claim 1, in which said energy source is located behind said window at the side of the housing opposite to the window.
3. A gas detector for use in an atmosphere where it is known that only one ultraviolet ray absorbing gas may be present in an amount that can readily be detected, said detector comprising a housing provided with a window in one side that filters out ultraviolet rays, a chamber in the housing for receiving a gas sample that may contain a certain ultraviolet ray absorbing gas, said chamber being provided in one side with an ultraviolet energy transmitting window adjacent said housing window, means for positioning outside of said chamber window a thin strip of material color-sensitive to ultraviolet rays, a constant source of ultraviolet energy in a position to direct its rays through the chamber and its window to change the color of the strip, and color standards exposed to view beside the housing window for matching with the color of said strip after a predetermined exposure time, whereby to indicate whether said ultraviolet ray absorbing gas is present in the chamber and its concentration therein.
References Cited in the file of this patent UNITED STATES PATENTS 1,597,487
I St. Clair Aug. 24, 1926 1,997,356 Bryant Apr. 9, 1935 2,576,616 Livingston et a1. Nov. 27, 1951 2,621,297 Obermaier Dec. 9,- 1952 2,624,011 Stern Dec. 30, 1952 2,680,816 Stein June 8,1954
US402120A 1954-01-04 1954-01-04 Gas detector Expired - Lifetime US2891164A (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1597487A (en) * 1924-12-26 1926-08-24 Gen Electric Recording device
US1997356A (en) * 1931-02-04 1935-04-09 Beryl B Bryant Invisible radiation, detection, and utilization
US2576616A (en) * 1949-09-20 1951-11-27 Livingston Ralph Monitor for fission gases
US2621297A (en) * 1946-02-23 1952-12-09 Illinois Testing Laboratories Apparatus for measuring vapor content of gas
US2624011A (en) * 1951-03-27 1952-12-30 Kurt G Stern Self-developing pocket radiation dosimeter
US2680816A (en) * 1951-03-12 1954-06-08 Kurt G Stern Film badge radiation detector

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1597487A (en) * 1924-12-26 1926-08-24 Gen Electric Recording device
US1997356A (en) * 1931-02-04 1935-04-09 Beryl B Bryant Invisible radiation, detection, and utilization
US2621297A (en) * 1946-02-23 1952-12-09 Illinois Testing Laboratories Apparatus for measuring vapor content of gas
US2576616A (en) * 1949-09-20 1951-11-27 Livingston Ralph Monitor for fission gases
US2680816A (en) * 1951-03-12 1954-06-08 Kurt G Stern Film badge radiation detector
US2624011A (en) * 1951-03-27 1952-12-30 Kurt G Stern Self-developing pocket radiation dosimeter

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